Expandalbe spinal implant and flexible driver

ABSTRACT

Expandable spinal implants and drivers connected by a bendable joint are disclosed. The flexible connector allows the implant and driver to move to different angular orientations with respect to each other, and to apply rotational force or torque from the driver to the implant and its expansion mechanism. During insertion of an implant into the desired position, the driver may be oriented in the same or different direction than the long axis of the implant. After the spinal implant is placed in the desired position, the driver is used to expand the implant in selected dimensions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/525,944, filed on Jun. 18, 2012 which claims the benefit of U.S.Provisional Patent Application Ser. No. 61/498,279 filed Jun. 17, 2011and U.S. Provisional Patent Application Ser. No. 61/499,855 filed Jun.22, 2011, all of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to spinal surgery, such as spinalfixation, and more particularly relates to expandable spinal implantsand flexible drivers for positioning and expanding the implants.

BACKGROUND INFORMATION

Spinal implant surgery may be performed by a posterior lumbar interbodyfusion (PLIF) approach, a transforaminal lumbar interbody fusion (TLIF)approach, or an extreme lateral interbody fusion (XLIF) approach. Inthese procedures, implants are inserted in desired positions in relationto the spine. Current spinal implant designs require an end approachdeployment mechanism that is not satisfactory for certain procedures.For example, with scoliosis in the thoracolumbar spine, an orthogonalapproach is often not possible. Additionally, with TLIF approachesutilizing expandable implants, the deployment has to be performed afterthe implant, e.g., cage or intervertebral spacer, has been turned insidethe disk space. This prevents access to adjust the height of the implantafter the implant has been turned, and makes extraction or removalproblematic.

Current expandable implant designs are limited to PLIF type ofapproaches because the implants cannot be turned or collapsed. However,with PLIF approaches, there may be a risk that the expanded implant orcage extrudes back into the nerves of the spinal canal along thedirection of its original insertion. In contrast, when a spacer isinserted with a TLIF approach, it is turned such that the trajectory isalong the wide axis (side-to-side) of the vertebral body and the implantcannot migrate out backwards into the spinal canal.

SUMMARY OF THE INVENTION

The present invention provides expandable spinal implants and flexibledrivers connected by a bendable joint that allow surgeons moreflexibility when performing spinal surgeries. The connection between thedriver and the implant includes a bendable joint, such as a helical hightorque spring, that allows the implant and driver to move to differentangular orientations with respect to each other, and to apply rotationalforce or torque from the driver to the implant and its expansionmechanism. During insertion of an implant into the desired position, thedriver may be oriented in a direction different than the long axis ofthe implant. After the spinal implant is placed in the desired position,the driver is used to expand the implant in selected dimensions. Incertain embodiments, the implants may include separate endplates whichare connected by a mechanical connection which allows expansion orcontraction. The endplates may be adjusted by the driver in parallel oroblique, or in kyphosis or lordosis, compared to the originalconfiguration of the implant.

An aspect of the present invention is to provide a surgical instrumentcomprising a driver, an expandable spinal implant, and a flexibleconnector connected to the driver and the implant, wherein the flexibleconnector is rotatable by the driver to expand the spinal implant.

Another aspect of the present invention is to provide a surgicalinstrument comprising a driver having a proximal end and a distal end,and a flexible connector releasably attached to the distal end of thedriver, wherein the flexible connector is structured and arranged toengage and expand a spinal implant when torque is applied to theflexible connector from the driver.

A further aspect of the present invention is to provide an expandablespinal implant comprising upper and lower plates expandable away fromeach other, an expansion mechanism structured and arranged to move theupper and lower plates away from each other, and a flexible connectorengageable with the expansion mechanism.

Another aspect of the present invention is to provide a method ofpositioning and expanding a spinal implant in a patient. The methodcomprises grasping the implant with a driver in an aligned insertionorientation, positioning the implant in the patient at a desiredposition while rotating the implant from the aligned insertionorientation to an angled orientation, expanding the implant with thedriver while the implant is in the angled orientation, and disengagingthe driver from the implant.

These and other aspects of the present invention will be more apparentfrom the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a TLIF spinal procedure in which an implant isinitially inserted in one orientation, and then rotated into the desiredposition in relation to the spinal vertebrae.

FIG. 2 is a partially schematic top view of an implant, driver andflexible connector, showing the arrangement of the components during aninitial insertion stage, and also showing the arrangement of thecomponents during a subsequent expansion stage (in phantom), inaccordance with an embodiment of the invention.

FIG. 3 is a partially schematic top view, and FIGS. 4 and 5 arepartially schematic side views, illustrating engagement between a driverand an expandable implant in accordance with an embodiment of thepresent invention.

FIG. 6 is a partially schematic top view, and FIG. 7 is an enlargedportion of FIG. 6, illustrating an intermediate stage of a TLIF spinalprocedure utilizing an expandable implant, driver and flexible connectorin accordance with an embodiment of the present invention.

FIG. 8 is a partially schematic top view illustrating a TLIF spinalprocedure in which an expandable implant has been placed in its finalposition and may be expanded using a driver and flexible connector inaccordance with an embodiment of the present invention.

FIG. 9 is a partially schematic side view of an expandable implant andflexible connector in accordance with an embodiment of the invention.

FIG. 10 is a partially schematic side view of an expandable implant andflexible connector in accordance with another embodiment of theinvention.

FIG. 11 is a partially schematic side view of an expandable implant andflexible connector in accordance with a further embodiment of theinvention.

FIG. 12 is a partially schematic side view of an expandable implant andflexible connector in accordance with another embodiment of theinvention.

FIG. 13 is a partially schematic exploded end perspective view showing arelease mechanism for disengaging a driver from a flexible connector inaccordance with an embodiment of the invention.

DETAILED DESCRIPTION

The present invention provides apparatus and methods for surgicalprocedures in which an expandable implant is positioned and deployed ina patient by means of a driver and a flexible connector. The driver maybe used to both position the implant in the desired location in relationto spinal vertebrae, and to expand the implant after it is positioned.The flexible connector transfers torque from the driver to therebyexpand the implant, and is detachable from the driver or implant afterthe implant is expanded.

FIG. 1 schematically illustrates a TLIF spinal procedure in which anexpandable implant is initially inserted in one orientation, and thenrotated into the desired position in relation to the spinal vertebrae.As shown in FIG. 1, a spinal vertebra 5 comprising a vertebral body 6,transverse process 7, spinous process 8 and spinal canal 9 is subject toa TLIF implant procedure. An implant generally labeled as element 10 isinitially inserted between the transverse process 7 and spinous process8, while substantially avoiding the spinal canal 9. During an initialinsertion stage, the implant 10 a is oriented as shown with itslongitudinal or axial direction A corresponding to the initial directionof insertion I. Subsequently, the implant is moved to its final desiredposition, labeled as 10 b, in which the axial direction A of the implant10 b is aligned in a direction substantially transverse to the spinalvertebra 5. The bottom face of the implant 10 b may contact the anteriorone-third of the vertebral body 6, while the top face of the implant 10b contacts the vertebral end plates of an adjacent vertebra in the spine(not shown). As described above, the TLIF procedure illustrated in FIG.1 advantageously orients the implant 10 b along a longer dimension ofthe vertebral body 6, and in a direction that does not intersect thespinal canal 9.

FIG. 2 is a partially schematic illustration showing the initialarrangement of an implant 10 a, driver 20 and flexible connector 30during an implant procedure, such as a TLIF spinal procedure, inaccordance with an embodiment of the invention. FIG. 2 also shows thearrangement of the implant 10 b, driver 20 and flexible connector 30 (inphantom) after the implant 10 b has been positioned in its finallocation where the implant may be expanded. As shown in FIG. 2, theimplant 10 a is initially grasped by the driver 20, which has a shaft 21and a handle 22. The driver 20 includes a stationary arm 23 and apivoting arm 25, as more fully described below. Although not shown inFIG. 2, an axially movable sleeve may be provided around the shaft 21 toforce the pivoting arm 25 into the closed position (shown by the solidline) when the sleeve is extended away from the handle 22, and to allowthe pivoting arm 25 to move to the open position (shown in phantom) whenthe sleeve is retracted toward the handle 22.

As further shown in FIG. 2, the flexible connector 30 releasably couplesthe driver 20 to the implant 10 a, 10 b. In the embodiment shown, theflexible connector 30 has a proximal end 31 connected to the driver 20by means of a releasable engagement mechanism 27. The flexible connector30 also has a distal end 32 connected to the implant 10 a. As shown inphantom in FIG. 2, the implant may be moved to the position labeled as10 b while the pivoting arm 25 has been rotated away from engagementwith the implant 10 b, and the flexible connector 30 bends but remainsconnected to the driver 20 and insert 10 b.

In certain embodiments, the flexible connector 30 comprises a helicalspring having sufficient flexibility to bend laterally, but sufficienttorsional stiffness to transfer torque from the driver 20 to the implant10 during the expansion operation. For example, the flexible connector30 may comprise a double helical spring or a double start spring withtwo elements, one wound clockwise and one wound counterclockwise. Such acounterwound double helical arrangement may add torsional stability toprevent buckling or permanent deformation when the spring is tensionedwith high forces. Examples of flexible helical couplings that may beadapted for use in accordance with the present invention includecommercially available helical springs sold under the designationHeli-Cal by Helical Products Company, Inc. The flexible connector 30 mayhave any suitable dimensions, for example, a length of from 3 to 50 mm,and an outer diameter of from 1 to 10 mm.

FIGS. 3-5 schematically illustrate an arrangement of an expandableimplant 10 and a driver 20. As shown in the top view of FIG. 3, theshaft 21 of the driver 20 has a distal end including a stationary arm 23and a pivoting arm 25. The stationary arm 23 includes a grip tooth 24comprising an extended ridge having a generally V-shaped cross section.The pivoting arm 25 includes a similar grip tooth 26. As shown in FIG.3, each of the grip teeth 24 and 26 engage a grip recess 18 in theimplant 10, comprising a generally V-shaped groove running verticallyfrom the top to bottom of the insert 10.

FIGS. 4 and 5 are side views schematically illustrating expansion of theimplant 10. The implant 10 includes an upper plate 11 and a lower plate12 that may be expanded away from each other from a contracted positionas shown in FIG. 4 to an expanded position as shown in FIG. 5. Forpurposes of illustration, the pivoting arm 25 is not shown in FIG. 4 or5. As most clearly shown in FIG. 5, as well as in FIG. 3, when the upperand lower plates 11 and 12 expand away from each other, the grip tooth24 on the stationary arm 23 may remain engaged with the respectivegrooves 18 in the upper and lower plates 11 and 12. In this manner, thestationary arm 23 of the driver 20 may remain engaged with the implant10 not only during placement of the implant 10 in the desired locationwithin the spine, but also during subsequent expansion of the implant10.

FIGS. 6 and 7 schematically illustrate an intermediate stage of a TLIFspinal procedure in which the implant 10 has been inserted into theregion of the anterior one-third of the vertebral body 6, and is beingrotated toward its final transverse position. The trajectory of theimplant 10 starts approximately parallel to the direction of the twoadjacent spinal pedicles on the ipsilateral side of the spine. As thespinal implant 10 is rotated it is turned by the implant driver 20 intoa position such that the long axis of the implant is in the translateralor transverse axis. As shown most clearly in the enlarged view of FIG.7, the stationary arm 23 and its grip tooth 24 may remain engaged in therespective grip recesses 18 of the implant. However, the pivoting arm 25has been rotated to a position as shown in which its grip tooth 26 hasdisengaged from its corresponding grip recesses 18 in the insert 10.Although the grip tooth 26 of the pivoting arm 25 has been disengaged,contact may still be maintained between an inner surface of the pivotingarm 25 and an end corner of the implant 10. As further shown in FIG. 7,at this stage of the procedure, the flexible connector 30 bends but isstill secured to both the driver 20 and implant 10. In certainembodiments, the flexible connector 30 may also expand or contract alongits longitudinal axis, e.g., the connector 30 may comprise a helicalspring that extends and/or compresses during stages of the procedure.

FIG. 8 illustrates a subsequent stage of a TLIF spinal procedure inwhich the implant 10 b is located at its desired transverse position inrelation to the anterior one-third of the vertebral body 6. The longaxis of the implant 10 b is in the transverse orientation, i.e., theline bisected by the anatomic transverse and coronal planes. In thisposition, the grip tooth 24 of the stationary arm 23 may still remain incontact with the corresponding grip recesses 18 of the implant 10 b,however, the pivoting arm 25 may no longer contact the implant 10 b.During the stages shown in FIGS. 6-8, the stationary arm 23 may be usedin various ways to push or otherwise force the implant into position.For example, instead of maintaining contact between the grip tooth 24and the grip recesses 18 during the entire procedure, the arm 23 may bemanipulated by the surgeon in any desired manner to contact variousparts of the implant 10 with various parts of the arm 23 to move theimplant into the desired position.

After the implant 10 b has been moved into position as shown in FIG. 8,torque may be applied to the driver 20 to rotate the flexible connector30 in order to expand the implant 10 b, as more fully described below.After the expansion step is completed, the driver 20 is disengaged fromthe implant 10 b. In one embodiment, the driver 20 is disengaged byreleasing the flexible connector 30 from the driver 20. In anotherembodiment, the driver 20 is disengaged by disengaging the flexibleconnector 30 from the implant 10 b.

FIGS. 9-12 schematically illustrate embodiments of expandable implants10 in accordance with the present invention. In the embodiment shown inFIG. 9, the implant 10 includes upper and lower plates 11 and 12comprising angled expansion ramps 13 on their inwardly facing surfaces.A threaded expansion rod 14 extends along the longitudinal axis of theimplant 10 in the region between the upper and lower plates 11 and 12.Internally threaded expansion wedges 15 are threaded onto the expansionrod 14. The threaded expansion rod 14 may be rotated around itslongitudinal axis by turning the flexible connector 30. Rotation of theflexible connector 30, and the resultant rotation of the threadedexpansion rod 14, causes the internally threaded expansion wedges 15 tomove axially along the rod 14 with their upper and lower exteriorsurfaces sliding along the expansion ramps 13. When the wedges 15 movetoward each other, the upper and lower plates 11 and 12 expand away fromeach other. While the expansion wedges 15 may be have cross-sectionalshapes that are circular or otherwise rounded, in a preferredembodiment, the expansion wedges 15 have square or rectangular crosssections that prevent the wedges from rotating around their centrallongitudinal axes. In this embodiment, the expansion ramps 13 maycomprise substantially flat surfaces contacting correspondingly flatsurfaces of the expansion wedges 15.

In the embodiment shown in FIG. 10, the upper and lower plates 11 and 12of the implant 10 have a similar configuration as shown in theembodiment of FIG. 9. However, the implant 10 has generally conicalexpansion wedges 17 that are externally threaded, and an expansion rod16 is not threaded. In this embodiment, the expansion ramps 13 arepreferably concave with conical surfaces that contact the threads of theconical externally threaded wedges 17. In this embodiment, thecross-sectional shape of the expansion rod 16 may be non-circular, andthe externally threaded wedges 17 may have correspondingly shaped holesextending axially therethrough with sufficient clearance for the wedges17 to axially slide along the expansion rod 16. In this manner, theexternally threaded wedges 17 may be free to slide along the axiallength of the expansion rod 16, but are constrained to rotate with theexpansion rod 16 when the expansion rod 16 is rotated around itslongitudinal axis. Rotation of the flexible connector 30 causes theexpansion rod 16 and externally threaded wedges 17 to rotate aroundtheir longitudinal axes, while the wedges 17 are free to slide along theaxial length of the expansion rod 16. Contact between the externalthreads of the wedges 17 and the conically shaped inner surfaces of theexpansion ramps 13 causes the wedges 17 to move axially toward eachother, which results in expansion of the upper and lower plates 11 and12 away from each other.

The embodiment shown in FIG. 11 is similar to the embodiment shown inFIG. 9, except the expansion ramps 13 a of the upper and lower plates 11and 12 are oriented in opposite directions, and the wedges 15 a arelikewise oriented differently. In this embodiment, rotation of theflexible connector 30 causes the wedges 15 a to move away from eachother along the longitudinal axis of the threaded expansion rod 14. Asthe wedges 15 a move away from each other, their exterior surfaces slideagainst the interior surfaces of the expansion ramps 13 a, therebyforcing the upper and lower plates 11 and 12 away from each other.

As shown in FIGS. 9-11, the distal end 32 of the flexible connector 30is attached to one end of the expansion rod 14 or 16. It is noted thatin the embodiments shown in FIGS. 9-11, the flexible connector 30 isillustrated as bending in a downward direction, however, it is to beunderstood that the flexible connector 30 may also bend in otherdirections, for example, into the page and/or out of the page in FIGS.9-11. In the embodiments shown, the distal end 32 of the flexibleconnector 30 includes a hexagonal recess 34 configured to receive thehead of a releasable engagement mechanism 27 of the driver 20, as morefully described below. In the embodiment shown, the distal end 32 of theflexible connector 30 may be permanently secured to the end of theexpansion rod 14 or 16, while the proximal end 31 of the flexibleconnector 30 may be releasably engaged with the driver 20.Alternatively, the distal end 32 may be releasably engaged with theexpansion rod 14 or 16, while the proximal end 31 may remain engagedwith the driver 20. For example, the distal end 32 of the flexibleconnector 30 may have a hex-head projection or recess that matinglyengages a corresponding hex-head recess or projection at the end of theexpansion rod 14 or 16. Such a hex-head connection may be sufficientlytight such that the connection is maintained during the steps ofinserting, positioning, and expanding the implant, but may be disengagedafter the implant is expanded by pulling the driver back with sufficientforce remove the hex-head projection from the recess.

FIG. 12 schematically illustrates another embodiment of an expandableimplant 10 in which the upper and lower plates 11 and 12 are expandedaway from each other by means of a distractor paddle 116 having an outercam surface that contacts inner surfaces of the upper and lower plates11 and 12 and forces them away from each other when the paddle 116 isrotated around its longitudinal axis. The upper and lower plates 11 and12 include expansion ramps 113 having surfaces that engage expansionwedges 15 a and 15 b. During the expansion procedure, the distractorpaddle 116 is rotated to spread the upper and lower plates 11 and 12away from each other, then a pusher 118 is used to move the firstexpansion wedge 115 a into a desired axial location where contactbetween the outer surface of the expansion wedge 115 a and the expansionramps 113 results in the desired amount of expansion of the upper andlower plates 11 and 12. Next, the distractor paddle 116 may be rotatedby the paddle shaft 117 to a position in which there is sufficientclearance between the distractor paddle 116 and the inner surfaces ofthe upper and lower plates 11 and 12 to allow the distractor paddle 116to be at least partially removed from the region between the upper andlower plates 11 and 12. The paddle shaft 117 is thus used to rotate andaxially move the distractor paddle 116. Upon removal of the distractorpaddle 116, the interior space between the upper and lower plates 11 and12 may be packed with bone material or the like in order to facilitatefusion of the implant 10 into the spinal structure. After the interiorspace is packed with material, the second expansion wedge 115 b may bemoved into a desired axial position by inserting it through the proximalend of the implant 10. The wedge 115 b may be placed with a screwdriveror other tool (not shown) which rotates the wedge 115 b 90 degrees afterit is inserted deep into the proximal end of the central cavity of theimplant 10. The proximal wedge 115 b may have an oblong or ellipticalcross-sectional shape. The proximal wedge 115 b may be inserted past theproximal ramp steps or teeth, and then rotated 90 degrees such that itslargest dimension of the ellipse is from cephalad to caudad. Theproximal wedge 115 b may then be pulled toward the ipsilateral open endof the implant until the smallest ramp is engaged or tight. The proximalwedge 115 b may thus be pulled away from the other wedge 115 a, and thenrotated around its longitudinal axis to contact the expansion ramps 113of the upper and lower plates 11 and 12. The expansion wedges 115 a and115 b may have non-circular cross sections which facilitate placement ofthe wedges in their desired axial locations, and retention in thosepositions in contact with the expansion ramps 113.

The dimensions used for the various components of the expandableimplants 10 may be selected as desired. For example, a typical implant10 may expand 10 percent to 100 percent of its original compact height,e.g., an implant may have a compact height of 8 mm and an expandedheight of 12 mm. Any suitable length of implant may be used, forexample, from 10 to 80 mm, e.g., 50 mm.

In the embodiments shown in FIGS. 9-12, the expansion ramps 13, 13 a and113 may be sized and arranged as desired. For example, each expansionramp 13, 13 a, 113 may have a dimension of 1 mm high and 1 mm in width,with a 10 to 15 degree ramp angle. In certain embodiments, the ramps maybe used to incrementally raise the height of an implant, e.g., from 8 mmto 9 mm to 10 mm to 11 mm to 12 mm in succession. The upper and lowerplates 11 and 12 of the implants 10 may have openings of suitable sizesthat allow bony ingrowth through the fusion cage, e.g., approximately 5mm by 20 mm in size.

The wedges, rods and other components of the expansion mechanisms may bemade of any suitable material such as titanium, while the upper andlower prosthetic endplates 11 and 12 may be made ofpoly-ether-ether-ketone (PEEK) or other suitable materials. Thecomponents of the driver 20 and flexible coupling 30 may be made ofsuitable materials such as stainless steel, titanium, and the like.

In certain embodiments, the expandable implants may be manufactured ofknown radiolucent material to allow radiographic visualization of thebone graft healing and incorporation. The flexible driver allows thesurgeon to reference the radiolucent implant orientation via a moreconstrained and predictable junction. A more secure linkage makes iteasier to exchange preparation instruments, soft tissue protectivecannulas, trochars, particularly while inserting implants overguidewires.

FIG. 13 schematically illustrates a release mechanism 27 for engagingand disengaging the driver 20 from the flexible connector 30. It isnoted that the various components are not drawn to scale in FIG. 13, butare provided for illustration purposes. In the embodiment shown, therelease mechanism 27 comprises a hex-head connector including radiallymovable engagement members or jaws 28. The outer surfaces of the jaws 28are configured to engage respective inner surfaces of the hex headrecess 34 of the flexible connector 30. When the jaws 28 are insertedinto the recess 34 and forced radially away from each other, they engageand are secured in the recess 34. An axially movable rod plunger 29 isused to force the jaws 28 radially away from each other by insertion ofits tapered head into opposing semi-circular channels in the interiorsurfaces of the jaws 28. The rod plunger 29 is axially movable insidethe cannulated driver shaft 21. Although not shown in FIG. 13, the jaws28 may be biased radially towards each other, for example, through theuse of tension springs (not shown). Thus, when the rod plunger 29 isretracted along its longitudinal axis away from the jaws 28, the jaws 28collapse toward each other, thereby disengaging their outer surfacesfrom the recess 34 of the flexible connector 30.

Although not shown in FIG. 13, the rod plunger 29 can also be threadedto create a smoother insertion without a need for hammering or impactionforce. Although a hex-head connection using two radially movable jaws isshown in FIG. 13, it is to be understood that any other suitable type ofreleasable coupling may be used in accordance with the presentinvention. For example, instead of two jaws 28 as shown in FIG. 13,three, four, five, six, or more radially expandable jaws or pivot armsmay be used. Furthermore, although a hexagonal recess 34 is shown inFIG. 13, any other suitable recess configuration could be used, such assquare, rectangular, triangular, oval and the like. Although the driver20 is releasably attached to the flexible connector 30 in the embodimentshown in FIG. 13, the flexible connector 30 may alternatively bereleasably attached to the implant, e.g., by a coupling similar to thatshown in FIG. 13 with a flexible rod plunger extending through acannulated central opening through the flexible connector 30, atight-fitting hex head connection that can be disengaged after theimplant is expanded by pulling the driver and flexible connector awayfrom the expanded implant with sufficient force, or the like.

The instruments of the present invention allow an implant to beoptimally positioned before it is expanded. For example, a TLIF implantcan be placed at an angle of up to 90 degrees from the posterior angleof insertion. Such a procedure allows a minimally invasive approach, asthe incision and exposure do not have to be extended to allowmanipulating or turning the expandable implant. This allows moving aTLIF implant into the preferred direct transverse orientation beforeopening.

In certain embodiments, the invention allows for expansion of anexpandable XLIF implant with minimally invasive exposure. Often with adeformity, or with multiple procedures performed through the same smallincision, the orientation of the interbody fusion changes as thedeformity is reduced. The angle of performance of the XLIF and the diskspace changes by the end of the case. This is common especially whendealing with L4-L5 and especially when dealing with the reduction of ascoliotic deformity. The flexible driver of the present invention allowsfor fine tuning, readjustment, backing off, re-expansion and balancingthe expansion between the multiple XLIF implants at the end of theprocedure.

The flexible driver of the present invention may be used in other typesof minimally invasive spine surgery. In such MIS procedures, theapproach is through a tube, narrow corridor, or confined space. Thisputs a premium on screwing, drilling, tapping, cutting screw threads,and performance of other maneuvers through a confined corridor withoutthe ability to alter the angle of trajectory of the tool shaft. Theflexible driver of the present invention helps solve this mechanicalchallenge by applying a rotational force at an angle from the insertiondirection.

In certain embodiments, anchorage of a stand alone anterior lumbarinterbody fusion (STALIF) type cages or interbody spacers is facilitatedby an angled driver with a helical spring flexible component. This isparticularly useful as the implant surgery becomes more minimallyinvasive.

In certain types of procedures, two expandable implants may bepositioned side by side in the intervertebral disk space. If theexpandable implant that is anterior is expanded and the posteriorexpandable implant is collapsed then this would increase and adjust theamount of spinal lordosis. On the contrary, if the reverse occurs withthe anterior implant collapsing and the posterior implant expanding thenthis would increase the amount of kyphosis.

In certain other types of procedures, two expandable implants may beplaced laterally end-to-end and individually adjusted. The expandableimplants could adjust the amount of coronal balance, and scoliosiscorrection could be adjusted after implant insertion at multiple levelsbut before closing the skin. By adjusting and expanding the implantsdifferentially, the spine can tilt left or right. Thus, the functionalspinal unit can be used to correct scoliosis apex toward the left or theright. The functional spinal units with expandable implants may bestacked one above another such as from T12 to L3 in order to correct athoracolumbar scoliosis.

Whereas particular embodiments of this invention have been describedabove for purposes of illustration, it will be evident to those skilledin the art that numerous variations of the details of the presentinvention may be made without departing from the invention as defined inthe appended claims.

What is claimed is:
 1. A surgical instrument comprising: a driver; anexpandable spinal implant; and a flexible connector connected to thedriver and the implant, wherein the flexible connector is rotatable bythe driver to expand the spinal implant.
 2. The surgical instrument ofclaim 1, wherein the flexible connector comprises a helical spring. 3.The surgical instrument of claim 2, wherein the helical spring comprisesa counterwound double helical spring.
 4. The surgical instrument ofclaim 1, wherein the flexible connector is releasably attached to thedriver.
 5. The surgical instrument of claim 4, wherein the flexibleconnector is permanently attached to the implant.
 6. The surgicalinstrument of claim 1, wherein the flexible connector is releasablyattached to the implant.
 7. The surgical instrument of claim 1, whereinthe driver further comprises at least one grip arm releasably engageablewith the implant.
 8. The surgical instrument of claim 1, wherein thedriver further comprises at least two grip arms releasably engageablewith the implant, and at least one of the grip arms is pivotable intoengagement with the implant.
 9. A surgical instrument comprising: adriver having a proximal end and a distal end; and a flexible connectorreleasably attached to the distal end of the driver, wherein theflexible connector is structured and arranged to engage and expand aspinal implant when torque is applied to the flexible connector from thedriver.
 10. The surgical instrument of claim 9, wherein the distal endof the driver comprises a hex-head connector including at least tworadially expandable engagement members releasably engageable with theflexible connector.
 11. A method of positioning and using a surgicalinstrument in a patient comprising: grasping an implant with a driver inan aligned insertion orientation, the driver having a proximal end and adistal end; a flexible connector releasably attached to the distal endof the driver, wherein the flexible connector is structured and arrangedto engage and expand a spinal implant; positioning the implant in thepatient at a desired position while rotating the implant from thealigned insertion orientation to an angled orientation; expanding theimplant with the driver while the implant is in the angled orientation;and disengaging the driver from the implant.
 12. The method of claim 11,wherein the driver and implant are releasably connected to each other bya flexible connector.
 13. The method of claim 12, wherein the implant isexpanded by rotating the driver to thereby apply torque through theflexible connector to an expansion mechanism in the implant.